At a time when peak numbers of immigrants are becoming eligible to naturalize, complexities in the occurrence and timing of naturalization are unknown. Certain recent immigrants, e.g., Asians, have appeared to be more likely to naturalize and to do so more quickly than others, especially Mexicans, but duration controls and heterogeneity specificity are needed to most accurately discern similarities and differences among immigrants of various origins in making the transition to citizen. The proposed project creates immigration to naturalization event histories for legal immigrant cohorts entering the United States from 1978-1991. The resulting public use files will be comparable to two existing files for the 1977 and 1982 cohorts. Drawing on rich information about characteristics at the time of immigration and about length of time to naturalization, a series of analyses will assess the relative effects of demographic, origin, vintage, duration, settlement contexts, social capital, and historical variables on the occurrence of naturalization.